Integrated circuit (“IC”) packages typically include an integrated circuit die that is mounted on and electrically attached to a leadframe. The electrical connections between the die and leadframe are often made by wire bonding in which a thin conductor wire is bonded at one end to a contact on the die and at the other end to a lead of the leadframe. The leadframe, die and bond wires are usually encapsulated in a protective, nonconductive block of material, such as epoxy. Portions of the leadframe are exposed through the bottom wall and/or sidewalls of the encapsulating block to enable electrical connection of the die to other electronics and/or to facilitate the transfer of heat from the IC die to the surrounding environment.
In an integrated circuit sensor package the die in the package is a sensor die that is adapted to sense a physical parameter of the surroundings of the IC sensor package. For example in a capacitive type humidity sensor a thin polymer film is attached to a surface of an IC die and is connected to electrical circuitry within the die. Changes in humidity affect the amount of moisture absorbed by the polymer film. Moisture absorption causes a change in the capacitance of the film. This change in capacitance is measured by the die circuitry and is representative of the humidity of the air. To make such an IC sensor package, the polymer film attached to the die must be exposed to the surrounding air.